#!/bin/bash
#
# Developed by Fred Weinhaus 11/17/2016 .......... revised 9/11/2021
#
# ------------------------------------------------------------------------------
# 
# Licensing:
# 
# Copyright © Fred Weinhaus
# 
# My scripts are available free of charge for non-commercial use, ONLY.
# 
# For use of my scripts in commercial (for-profit) environments or 
# non-free applications, please contact me (Fred Weinhaus) for 
# licensing arrangements. My email address is fmw at alink dot net.
# 
# If you: 1) redistribute, 2) incorporate any of these scripts into other 
# free applications or 3) reprogram them in another scripting language, 
# then you must contact me for permission, especially if the result might 
# be used in a commercial or for-profit environment.
# 
# My scripts are also subject, in a subordinate manner, to the ImageMagick 
# license, which can be found at: http://www.imagemagick.org/script/license.php
# 
# ------------------------------------------------------------------------------
# 
####
#
# USAGE: textdeskew [-n number] [-r radius ] [-m metric] [-a attenuate]  
# [-l logval] [-c color] [-t trimval] [-p padval] infile outfile1 [outfile2]
#
# USAGE: textdeskew [-h or -help]
# 
# OPTIONS:
#
# -n     number        stopping number of maxima; integer>1; default=20
# -r     radius        radius for masking out peaks; integer>0; default=7
# -m     metric        compare metric; any valid IM metric; default=rmse
# -a     attenuate     attenuation percent for the brightness near the 
#                      center of the FFT spectrum; 0<integer<=100; default=85
# -l     logval        value for log when converting the FFT magnitude to 
#                      spectrum; integer>0; default=1000000
# -c     color         background color for deskewed image; any valid IM 
#                      color is allowed; default=white
# -t     trimval       trim fuzz value; 0<=float<=100; default=no trim
# -p     padval        padding added to output; integer>=0; default=no padding
# -T     thresh        threshold on image std; if too low abort since not 
#                      enough lines of text for FFT processing; 0<int<100;
#                      default=5 (percent).
# 
# An optional output image may be specified which will be the masked 
# FFT spectrum showing the locations of the peaks that define the line from  
# which the unrotation angle is determined.
#
###
# 
# NAME: TEXTDESKEW
# 
# PURPOSE: To unrotate (deskews) an image containing text.
# 
# DESCRIPTION: TEXTDESKEW unrotates (deskews) an image containing many rows 
# of text. If the meta data contain orientation information, then the image 
# will be auto-oriented first. The image is converted to the FFT spectrum 
# image and a list of peaks orthogonal to the rows of text are located. From 
# the list of peak coordinates a least square fit to a line is computed and   
# the orientation of the line is used to get the unrotation angle. The approach  
# will not be able to determine whether the text is right side up or up side  
# down. However, it should properly correct for rotations in the range of 
# -90<=rotation<90. Note that +90 will be upside down, since lines rotated 
# by 180 degrees are undistinguishable. The more lines of text, the better 
# the script works. If there are too few lines of text, the the script may 
# fail.
# 
# Arguments: 
# 
# -n number ... NUMBER of peaks to be found. Values are integers>1. 
# The default=20.
# 
# -r  radius ... RADIUS value for masking out peaks. Values are integers>0. 
# The default=20.
# 
# -m metric ... METRIC is the compare metric used to locate the maxima. 
# Any valid IM metric may be used. The default=rmse. This option is only 
# needed for Imagemagick versions less than 6.8.6-10.
# 
# -a attenuate ... ATTENUATE is the attenuation percent for the brightness 
# near the center of the FFT spectrum. This is used since the center of 
# the FFT spectrum is brighter than the outer regions. Attenuation linearly 
# ramps from the center to no attenuation at the edges of the spectrum. 
# Attenuating the center allows a longer linear distribution of found peaks, 
# which helps to better define the orientation line. However, it may introduce 
# more off-linear false peaks. Shorter lengths of text may require a different 
# attenuation. Values are 0<integer<=100. 100 means no center attenuation. 
# The default=85.
#
# -l logval ... LOGVAL is the value for log when converting the FFT magnitude  
# to the spectrum. Values are integers>0. The default=1000000.
# 
# -c color ... COLOR is the background color for deskewed image. Any valid IM 
# color is allowed. The default=white.
# 
# -t trimval ... TRIMVAL is the trim fuzz value (percent) for trimming the 
# output to its minimum bounding box. Values are 0<=floats<=100. The 
# default=no trimming.
# 
# -p padval ... PADVAL is the padding added to the output. Values are
# integers>=0. The default=no padding.
# 
# -T thresh ... THRESh is the threshold on image std. If too low abort, since  
# there is not enough lines of text for FFT processing. Values are in the 
# range 0<int<100. The default=5 (percent).
# 
# An optional output image may be specified which will be the masked 
# FFT spectrum showing the locations of the peaks that define the line from  
# which the unrotation angle is determined.
# 
# REQUIREMENTS: IM 6.5.4-7 or higher and the FFTW delegate library.
# 
# NOTE: Some versions of Imagemagick around 6.8.8-5 may not work due to a bug.
# 
# CAVEAT: No guarantee that this script will work on all platforms, 
# nor that trapping of inconsistent parameters is complete and 
# foolproof. Use At Your Own Risk. 
# 
######
#

# set default values
number=20			# number of peaks
radius=7			# mask radius
metric="rmse"		# compare metric
attenuate=85		# center intensity attenuation
logval=1000000		# value for log conversion of magnitude to spectrum
trimval=""			# trim fuzz value
padval=""			# pad amount
thresh=5			# threshold for text content

# set internal arguments
res_thresh=2		# threshold on residuals to filter points and refine regression
debug="false"		# show debug information

# set directory for temporary files
tmpdir="." 		# suggestions are tmpdir="." or tmpdir="/tmp"

dir="$tmpdir/TEXTDESKEW.$$"

mkdir "$dir" || errMsg "--- FAILED TO CREATE TEMPORARY FILE DIRECTORY ---"
trap "rm -rf $dir;" 0
trap "rm -rf $dir; exit 1" 1 2 3 15
#trap "rm -rf $dir; exit 1" ERR


# set up functions to report Usage and Usage with Description
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program
usage1() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^###/g;  /^#/!q;  s/^#//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}
usage2() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^######/g;  /^#/!q;  s/^#*//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}

# function to report error messages
errMsg()
	{
	echo ""
	echo $1
	echo ""
	usage1
	exit 1
	}

# function to test for minus at start of value of second part of option 1 or 2
checkMinus()
	{
	test=`echo "$1" | grep -c '^-.*$'`   # returns 1 if match; 0 otherwise
    [ $test -eq 1 ] && errMsg "$errorMsg"
	}


# function to do linear regression to find best fit line, rotation angle, and orthogonal residuals 
# see http://dep.fie.umich.mx/~lromero/my_papers/2014_TLS_ICMEE029.pdf
# y=ax+b; b=intercept and a=slope
# use line form of r,phi
# r=x*cos(phi)+y*sin(phi) or y=-(x/tan(phi)) +r/sin(phi)
# do total least square fit to get phi and then use r=Xave*cos(phi)+Yave*sin(phi)
# then use previous line to get slope=-1/tan(phi) and intercept=r/sin(phi)
linearRegression() 
	{
	Arr="$1"
	regression_Arr=(`echo "${Arr[*]}" | awk \
	'BEGIN { FS = ","; RS = " "; pi = atan2(0, -1); }
	NF == 2 { x_sum += $1
			  y_sum += $2
			  xy_sum += $1*$2
			  x2_sum += $1*$1
			  y2_sum += $2*$2
			  num += 1
			  x[NR] = $1
			  y[NR] = $2
			}
	END { mean_x = x_sum / num
		  mean_y = y_sum / num
		  for (i = 1; i <= num; i++) {	
		  	  delx = (x[i]-mean_x)
		  	  dely = (y[i]-mean_y)
			  numerator += delx*dely
			  denominator += dely*dely - delx*delx
		  }
		  phi = 0.5*atan2(-2*numerator,denominator)
		  r = mean_x*cos(phi)+mean_y*sin(phi)
		  if ( sqrt(phi*phi) < 0.0001 ) {
		      angle = -90
		  }
		  else {
			  slope = -cos(phi)/sin(phi)
			  inter = r/sin(phi)
			  angle = (180/pi)*atan2(slope,1)
		  }
		  for (j = 1; j <= num; j++) {
		  	  delr = (x[j]*cos(phi)+y[j]*sin(phi)-r)
		  	  res_sq = delr*delr
		  	  sum_res_sq += res_sq
		  	  res = sqrt(delr*delr)
		  	  sum_res += res
			  print "Residual"j":"res
		  }	
		  res_ave = sum_res/num
		  res_std = sqrt((sum_res_sq/num)-(sum_res/num)**2)
		  print "res_ave:"res_ave
		  print "res_std:"res_std
		  print "phi:"phi
		  print "r:"r
		  print "Slope:"slope
		  print "Intercept:"inter
		  print "Angle:"angle
		}'`)

	rnum=${#regression_Arr[*]}
	if $debug; then
		echo ""
		echo "rnum=$rnum;"

		# list regression data
		for ((ii=0; ii<rnum; ii++)); do
		echo "${regression_Arr[$ii]}"
		done
	fi

	}

# test for correct number of arguments and get values
if [ $# -eq 0 ]
	then
	# help information
	echo ""
	usage2
	exit 0
elif [ $# -gt 21 ]
	then
	errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---"
else
	while [ $# -gt 0 ]
		do
		# get parameters
		case "$1" in
	  -h|-help)    # help information
				   echo ""
				   usage2
				   ;;
			-r)    # radius
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID RADIUS SPECIFICATION ---"
				   checkMinus "$1"
				   radius=`expr "$1" : '\([0-9]*\)'`
				   [ "$radius" = "" ] && errMsg "--- RADIUS=$radius MUST BE A NON-NEGATIVE INTEGER (with no sign) ---"
				   ;;
			-n)    # number
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID NUMBER SPECIFICATION ---"
				   checkMinus "$1"
				   number=`expr "$1" : '\([0-9]*\)'`
				   [ "$number" = "" ] && errMsg "--- NUMBER=$number MUST BE A NON-NEGATIVE INTEGER (with no sign) ---"
				   test=`echo "$number <= 2" | bc`
				   [ $test -eq 1 ] && errMsg "--- NUMBER=$number MUST BE A POSITIVE INTEGER GREATER THAN 1 ---"
				   ;;
		 	-m)    # metric
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID METRIC SPECIFICATION ---"
				   checkMinus "$1"
				   # test mode values
				   metric="$1"
				   metric=`echo "$metric" | tr "[:upper:]" "[:lower:]"`
				   case "$metric" in 
				   		ae) ;;
						fuzz) ;;
						mae) ;;
						mepp) ;;
						mse) ;;
						ncc) ;;
						pae) ;;
						psnr) ;;
						rmse) ;;
						*) errMsg "--- METRIC=$metric IS AN INVALID VALUE ---" 
					esac
				   ;;
			-a)    # attenuate
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID ATTENUATE SPECIFICATION ---"
				   checkMinus "$1"
				   attenuate=`expr "$1" : '\([0-9]*\)'`
				   [ "$attenuate" = "" ] && errMsg "--- ATTENUATE=$attenuate MUST BE A NON-NEGATIVE INTEGER (with no sign) ---"
				   test1=`echo "$attenuate < 1" | bc`
				   test2=`echo "$attenuate > 100" | bc`
				   [ $test1 -eq 1 -o $test -eq 2 ] && errMsg "--- ATTENUATE=$attenuate MUST BE A POSITIVE INTEGER BETWEEN 1 AND 100 ---"
				   ;;
			-l)    # logval
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID LOGVAL SPECIFICATION ---"
				   checkMinus "$1"
				   logval=`expr "$1" : '\([0-9]*\)'`
				   [ "$logval" = "" ] && errMsg "--- LOGVAL=$logval MUST BE A NON-NEGATIVE INTEGER (with no sign) ---"
				   ;;
			-c)    # color
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID COLOR SPECIFICATION ---"
				   checkMinus "$1"
				   color="$1"
				   ;;
			-t)    # trimval
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID TRIMVAL SPECIFICATION ---"
				   checkMinus "$1"
				   trimval=`expr "$1" : '\([0-9]*\)'`
				   [ "$trimval" = "" ] && errMsg "--- TRIMVAL=$trimval MUST BE A NON-NEGATIVE FLOAT (with no sign) ---"
				   test1=`echo "$trimval > 100" | bc`
				   [ $test1 -eq 1 ] && errMsg "--- TRIMVAL=$trimval MUST BE A FLOAT BETWEEN 0 AND 100 ---"
				   ;;
			-p)    # padval
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID PADVAL SPECIFICATION ---"
				   checkMinus "$1"
				   padval=`expr "$1" : '\([0-9]*\)'`
				   [ "$padval" = "" ] && errMsg "--- PADVAL=$padval MUST BE A NON-NEGATIVE INTEGER (with no sign) ---"
				   ;;
			-T)    # thresh
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID THRESH SPECIFICATION ---"
				   checkMinus "$1"
				   thresh=`expr "$1" : '\([0-9]*\)'`
				   [ "$thresh" = "" ] && errMsg "--- THRESH=$thresh MUST BE A NON-NEGATIVE FLOAT (with no sign) ---"
				   test1=`echo "$thresh > 100" | bc`
				   [ $test1 -eq 1 ] && errMsg "--- THRESH=$thresh MUST BE A FLOAT BETWEEN 0 AND 100 ---"
				   ;;
			 -)    # STDIN and end of arguments
				   break
				   ;;
			-*)    # any other - argument
				   errMsg "--- UNKNOWN OPTION ---"
				   ;;
			*)     # end of arguments
				   break
				   ;;
		esac
		shift   # next option
	done
	# get infile and outfile
	infile="$1"
	outfile1="$2"
	outfile2="$3"
fi

# test that infile provided
[ "$infile" = "" ] && errMsg "--- NO INPUT FILE SPECIFIED ---"


# test input image
convert -quiet "$infile" -auto-orient +repage $dir/tmpI.mpc ||
	errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAS ZERO SIZE ---"
	
# test amount of black (presumably text) in the image. Abort if too low
std_pct=`convert $dir/tmpI.mpc -alpha off -format "%[fx:100*standard_deviation]" info:`
#echo "std_pct=$std_pct"
std_test=`echo "$std_pct < $thresh" | bc`
[ $std_test -eq 1 ] && errMsg "--- FILE $infile HAS TOO FEW LINES OF TEXT (std=$std_pct%) ---"

# create spectrum image
# due to bug in FFT in Imagemagick around 7.0.10.61, explicitly set normalization to forward
convert $dir/tmpI.mpc -alpha off \
	-colorspace gray -define fourier:normalize=forward \
	-fft +delete -evaluate log $logval \
	$dir/tmpS.mpc

# attenuate spectrum by radial gradient
wxh=`convert -ping $dir/tmpI.mpc -format "%wx%h" info:`
convert $dir/tmpS.mpc \
	\( -size $wxh radial-gradient:"gray($attenuate%)-white" \) \
	-compose multiply -composite -auto-level -evaluate max 1 \
	$dir/tmpS.mpc	
 
# get quantumrange
qrange=`convert xc: -format "%[fx:quantumrange]" info:`

# get im version
im_version=`convert -list configure | \
	sed '/^LIB_VERSION_NUMBER */!d;  s//,/;  s/,/,0/g;  s/,0*\([0-9][0-9]\)/\1/g' | head -n 1`

if [ "$im_version" -ge "07000000" ]; then
	identifying="magick identify"
else
	identifying="identify"
fi

# colorspace RGB and sRGB swapped between 6.7.5.5 and 6.7.6.7 
# though probably not resolved until the latter
# then -colorspace gray changed to linear between 6.7.6.7 and 6.7.8.2 
# then -separate converted to linear gray channels between 6.7.6.7 and 6.7.8.2,
# though probably not resolved until the latter
# so -colorspace HSL/HSB -separate and -colorspace gray became linear
# but we need to use -set colorspace RGB before using them at appropriate times
# so that results stay as in original script
# The following was determined from various version tests using maxima.
# with IM 6.7.4.10, 6.7.6.10, 6.8.5.10
if [ "$im_version" -lt "06070606" ]; then
	cspace="RGB"
else
	cspace="sRGB"
fi

# set up use of -subimage-search
if [ "$im_version" -ge "06060306" ]; then
	subimagesearch="-subimage-search"
else
	subimagesearch=""
fi
	

# set up for using (new) %[max] or (old) %[maxima]
# notation changed somewhere between 6.7.4.10 and 6.7.7.7, but do not know where
test=`convert -quiet xc:white xc:black +append -format "%[maxima]" info:`
if [ "$test" != "" ]; then
	# old
	maximum="maxima"
else
	# new
	maximum="max"
fi


if [ "$im_version" -lt "06080610" ]; then
	flag=""
	for ((i=0; i<number; i++)); do
		val=`convert $dir/tmpS.mpc -format "%[$maximum]" info:`
		valpct=`convert xc: -format "%[fx:100*$val/$qrange]" info:`
		match=`compare -metric $metric $subimagesearch $dir/tmpI.mpc \( -size 1x1 xc:"gray($valpct%)" \) null: 2>&1`
		location=`echo $match | cut -d\  -f4`
		locArr[$i]=$location
		if $debug; then
			echo "$location gray=$valpct%"
		fi
		convert $dir/tmpS.mpc -fill black -draw "translate $location circle 0,0 0,$radius" $dir/tmpS.mpc
	done
else
	flag=""
	for ((i=0; i<number; i++)); do
		[ "$graphic" = "yes" ] && convert $dir/tmpI.mpc show:
		data=`$identifying -precision 5 -define identify:locate=maximum -define identify:limit=1 $dir/tmpS.mpc |
			tail -n +2 | tr -cs "[0-9,.]*" " " | sed 's/^ *//g'`
		location=`echo "$data" | cut -d\  -f3`
		valfrac=`echo "$data" | cut -d\  -f2`
		valpct=`convert xc: -format "%[fx:100*$valfrac]" info:`
		locArr[$i]=$location
		if $debug; then
			echo "$location gray=$valpct%"
		fi
		convert $dir/tmpS.mpc -fill black -draw "translate $location circle 0,0 0,$radius" $dir/tmpS.mpc
	done
fi



# do total (orthogonal) linear regression to fit set of points to line
linearRegression "${locArr[*]}"
angle=`echo ${regression_Arr[rnum-1]} | cut -d: -f2`
# set rotation to be correct for -90<=angle<90 (+90 will be upside downs)
rotation=`convert xc: -format "%[fx:$angle<0?-($angle+90):-($angle-90)]" info:`
rotation=`convert xc: -format "%[fx:abs($rotation)<0.00001?0:$rotation]" info:`

# remove outliers, if res_ave > res_thresh
res_ave=`echo ${regression_Arr[rnum-7]} | cut -d: -f2`
test1=`convert xc: -format "%[fx:$res_ave>$res_thresh?1:0]" info:`
if [ $test1 -eq 1 ]; then
	res_std=`echo ${regression_Arr[rnum-6]} | cut -d: -f2`
	res_std2=`convert xc: -format "%[fx:2*$res_std]" info:`
	if $debug; then
		echo "res_std=$res_std; res_std2=$res_std2;"
	fi
	k=0
	for ((j=0; j<number; j++)); do
		res=`echo ${regression_Arr[$j]} | cut -d: -f2`
		test2=`convert xc: -format "%[fx:$res>$res_std2?1:0]" info:`
		if $debug; then
			echo "res_$j=$res; res_std2=$res_std2; test2=$test2;"
		fi
		if [ $test2 -eq 0 ]; then
			locArr2[$k]="${locArr[$j]}"
			k=$((k+1))
		fi		
	done

	if $debug; then
		echo "newnum=${#locArr2[*]}"
		echo "${locArr2[*]}"
	fi
	
	# do another total (orthogonal) linear regression to fit filtered set of points to line
	linearRegression "${locArr2[*]}"
	angle=`echo ${regression_Arr[rnum-1]} | cut -d: -f2`
	# set rotation to be correct for -90<=angle<90 (+90 will be upside downs)
	rotation=`convert xc: -format "%[fx:$angle<0?-($angle+90):-($angle-90)]" info:`
	rotation=`convert xc: -format "%[fx:abs($rotation)<0.00001?0:$rotation]" info:`
	echo "Rotating Image $rotation degrees"
else
echo "Rotating Image $rotation degrees"
fi


# set up trimming
if [ "$trimval" != "" ]; then
	trimming="-fuzz $trimval% -trim +repage"
else
	trimming=""
fi

# set up padding
if [ "$padval" != "" ]; then
	padding="-bordercolor $color -border $padval"
else
	padding=""
fi

# do rotation to deskew
convert $dir/tmpI.mpc -background "$color" -rotate $rotation +repage $trimming $padding "$outfile1"
[ "$outfile2" != "" ] && convert $dir/tmpS.mpc "$outfile2"

exit 0



